Conveyor belt and a process for the manufacture thereof

ABSTRACT

A conveyor belt in which the rubber cover is bonded with the core impregnated with an adhesive, characterized in that the core is a nonwoven sheet consisting of a filamentary layer of longitudinally paralleled synthetic filaments or chemical filaments and web layers of random or carded staple fibers which are superposed on the top and bottom of the filamentary layer, said filamentary layer being composed of substantially nontwisted and noncrimped filaments, and the web layers being composed of crimped staple fibers, that the filamentary layer and the web layers are superposed and integrated by needling, that the nonwoven sheet is sufficiently impregnated with an adhesive, that the weight ratio of the filamentary layer to the web layers ranges 5:1 to 1:1 and that the said adhesive is of rubber-type, and a process for the manufacture thereof.

Unit

Inventors Katsukiyo Tanimoto;

Tamio Urakawa; Sotaro Itadani, all of Kurashiki, Japan App]. No. 794,248

Filed Jan. 27,1969

Patented Oct. 26, 1971 Assignee Kurashiki Rayon Co., Ltd.

Sazaku, Kurashiki, Okayama Prefecture, Japan Priorities Jan. 30,1968

Japan 43/5568;

June 27, 1968, Japan, N0. 43/54547 CONVEYOR BELT AND A PROCESS FOR THEMANUFACTURE THEREOF 13 Claims, 4 Drawing Figs.

U.S.C1 161/141, 74/232,161/81,161/85,161/152,161/154 Int. Cl B32b 3/18,B32b 5/08 Field of Search 161/141 [56] References Cited UNITED STATESPATENTS 2,633,227 3/1953 Hutchins. 161/144 2,793,150 5/1957 Deaves...161/144 3,154,462 10/1964 Smith 161/154 3,401,467 9/1968 Koester 161/154Primary Examiner-Morris Sussman Attorney-Sherman and Shalloway ABSTRACT:A conveyor belt in which the rubber cover is bonded with the coreimpregnated with an adhesive, characterized in that the core is anonwoven sheet consisting of a filamentary layer of longitudinallyparalleled synthetic filaments or chemical filaments and web layers ofrandom or carded staple fibers which are superposed on the top andbottom of the filamentary layer, said filamentary layer being composedof substantially nontwisted and noncrimped filaments, and the web layersbeing composed of crimped staple fibers, that the filamentary layer andthe web layers are superposed and integrated by needling, that thenonwoven sheet is sufficiently impregnated with an adhesive, that theweight ratio of the filamentary layer to the web layers ranges 5:1 to1:1 and that the said adhesive is of rubber-type, and a process for themanufacture thereof.

CONVEYOR BELT AND A PROCESS FOR THE MANUFACTURE THEREOF This inventionrelates to a conveyor belt and a process for the manufacture thereof.More particularly, the invention re lates to a conveyor belt having acore body fabric and outer rubber covers on its top and bottom, saidcore fabric construction comprisinga filamentary layer in which thefilaments are paralleled in the longitudinal direction, web layerssuperposed on its top and bottom, the layers of filaments and webstogether forming a needled sheet of nonwoven fabric, and the sheetserving as the core being sufficiently impregnated with an adhesive, andalso to a process for the manufacture thereof.

It is known that conveyor belts are made in numerous ways and of variousconstructions. Among known conveyor belts, some employ multi-ply corebodies formed by laminating several sheets of plain woven fabrics. Aconveyor belt of monopoly core, i.e. core of single woven fabric isimpractica ble, because it exhibits too great elongation and excessivepliability which means poor load carrying ability. Therefore, theelongation and pliability are suitably adjusted by combining severalsheets of woven fabric in the known conveyor belts. On the otherhand,.in such multi-ply constructions, sufficiently strong bonding isrequired between the rubber cover and core bodies and flexibility of thebelt is sacrified to a certain extent. Such multi-ply conveyor belts arefurthermore unsuitable for the use in the field where less longitudinalis required, since they have a relatively large elongation in saiddirection. Also the core body of such conveyor belt requires much laborin numbers of steps such as spinning, weaving, laminating several sheetsof woven fabric and clipping of the core for imparting adherabilitythereto with the rubber cover. Such conveyor belts are formed throughsteps of friction of rubber, and pressing of the rubber cover on thecore body. Thus their manufacturing procedures are time-consuming, andthe products, expensive.

Conveyor belts using the core in which staple fiber are mixed intomasticated rubber by roll blending are also known. However such beltsare not only insufficient in strength, but also exhibit excessively highelongation and low tear strength, because of the limitations incurred ontheir manufacturing conditions that the staple fibers to be mixed withmasticated rubber should not be any longer thanlO mm., and the amountthereof is at most l-20 percent to the rubber. Also their joiningability to metallic tools at the ends is unsatisfactory, which is anindeed serious defect.

The main object of the invention is, therefore, to provide a novel,monoply conveyor belt having a sheet of nonwoven fabric consisting of afilamentary layer and web layers as the core.

Still another object of the invention is to provide a conveyor beltwhich exhibits sufficiently high strength and low elongation in thelongitudinal direction.

A further object of the invention is to provide a novel process formanufacture of conveyor belts consisting of simpler steps compared withthe conventional methods requiring many steps and much labor.

Other many objects and advantages of the invention will become apparentfrom the following descriptions.

Conveyor belts are used as a combination of rubber cover and a suitablecore body selected according to the purpose of use. They are generallyclassified into low-, medium, and high-strength conveyor belts. Requiredperformances of the conventional lowand medium-strength conveyor beltsusing woven fabrics as the core are as follows:

i. That they exhibit high strength in the longitudinal direction ofbelt, such as 100-300 kg. per 1 cm. width of belt; the tension in use isapproximately one-tenth to one-sixteenth of the strength. The elongationin that case is preferably no more than 2 percent.

2. That the adherability of the core with rubber cover is at least 7 kg.per 2.5 cm. width.

3. That the belts possess flexibility; they should be able to resist theflexing of 100,000 times in the later described flexing test (cf.examples).

4. That the two ends of the conveyor belt can be easily joined.(Normally lacing is used for this purpose). The bonding efficiencyshould be at least 30 percent to the strength in longitudinal direction.

5. That the belts possess impact strength.

6. That the belts exhibit little fatigue during use. That is, theyshould exhibit little alteration in core strength, and little aging inthe adherability with rubber cover.

7. That the foregoing performances should show little deteriorationunder wet conditions.

The conveyor belts of the invention uses as the core single ply sheet ofnonwoven fabric composed of synthetic, chemical fibrous layer ofnontwisted and noncrimped filaments which are parallel in thelongitudinal direction of the belt, and carded or random web layers ofsynthetic, chemical staple fibers which are superposed on the twosurfaces (top and bottom) of the first filamentary layer. Thefilamentary layer and web layers are joined by needling, andsufficiently impregnated with an adhesive.

In the present specification and appended claims, nonwoven sheet isdefined to designate thefilamentary layer and the web layers joined byneedling, and core" means the nonwoven sheet impregnated with anadhesive.

Among the attached drawings, FIG. ll shows a fragmentary horizontalsection of a conveyor belt of the invention. FIG. 2 shows a fragmentaryhorizontal section of a conventional conveyor belt. FIG. 3 shows a planview of the needle employed for needling the filamentary layer and twoweb layers in accordance with the invention. And, FlG. d is an enlargedplan view of barb 25 of the needle.

Referring to FIG. 1, ll denotes rubber cover, 2 denotes web layers, 3 isthe filamentary layer, 4 denotes the filaments paralleled in thelongitudinal direction, and5 indicates the joined state offibers afterneedling of the filamentary layer 3 and web layer 2. The rubber cover land web layers 2 are adhered by pressing.

Referring to FIG. 2, ll is the rubber cover, and 112 is the core bodycomposed of woven fabric, 13 denoting woof and 14, warp. The core body12 consists of multiple plies, i.e., several sheets of woven fabricssuperposed one another, and is impregnated with an adhesive by dipping.The core 112 is furthermore bonded to the rubber cover II by pressing.

Referring now to FIG. 3, 21 is a shank, 22 is an intermediate blade, 23is the blade and 24, barb: Referring to FIG. 4, 33 is keep-up height, 34is the throat depth, 35 is the throat length, and 36 denotes undercutangle.

As the fiber material forming the filamentary layer and web layers inthe conveyor belt of the invention, synthetic, chemical fibers frompolyester, polyvinyl, polypropylene, polyamide and high tenacity rayon,etc. can be used.

The filamentary layer is formed of substantially nontwisted andnoncrimped filaments. Substantially nontwisted and noncrimped means thatthe filaments have not been subjected to twisting or crimping step withthe intention of imparting thereto, respectively, twist or crimp. Use oftwisted or crimped filaments is undesirable, since such deteriorates thelongitudinal strength and flexibility which are required of conveyorbelts, and furthermore objectionably increases the elongation.

The objects of the invention can be sufficiently achieved with the useof such filaments of the size conventionally produced. The preferredsize ranges l.4-5'7 deniers.

Whereas, the web layers are formed of carded or random webs of crimpedstaple fibers, with the use of conventional apparatus for makingnonwoven fabrics. The length of the staple fibers is not particularlycritical, but those of at least 40 mm., preferably 40-120 mm. showimproved intertwining property with the filamentary layer. The cutfibers of conventional size can be satisfactorily used, similarly to thecase of filaments.

The weight ratio of filamentary layer to web layers is variable to acertain extent, depending on the type of material used. It normallyranges, however, from l:l-5:l, preferably 23:l. When the weight ratio isless than 1/1 flexibility of the belt is impaired due to the excessivebulk of the web layers, and

when it is more than 5/1, intertwining effect of needling is hampered todeteriorate flexibility of the product. The weight of the filamentarylayer varies according to the intended strength and width of theconveyorbelt. With the increase in weight of filamentary layer,thickness of the layer increases, showing a tendency of flexibilitydeterioration. Accordingly, it is desirable to keep the weight offilamentary layer to the allowable minimum depending on on the intendedstrength of conveyor belt. Such minimum weight is advantageous also fromeconomical standpoint. it is normally no more than 900 g./m. preferablyno more than 800 g./m. It can be understood that the weight of the webscan be readily determined from the aforesaid weight ratio and specificweight of the filamentary layer.

The total thickness of the core body depends on the weights offilamentary layer and two web layers, as well as on the pressureemployed for pressing the rubber cover thereonto as the final step. Incase of manufacturing medium or low-strength belt in accordance withaccepted practice, the thickness is normally no more than approximately1.5 mm., preferably no more than 1.2 mm.

Needling is performed for the purpose of shape retention of the corebody. Either one of web layers and the filamentary layer may be firstneedled and then superposed with the other weblayer to be subjected tothe second needling, or both of the web layers may be superposed on thetop and bottom of filamentary layer to be needled only once. Obviouslythe needling can be given repeated number of times, so far as the layersto be needled are not damaged.

When an excessive needling is given to the filamentary layer alone, thefilaments are cut and longitudinal strength and elongation of the beltare impaired. Also if the excessive needling is given to the web layersalone, intertwining of fibers is strengthened and the web becomescompact. Because of this, even when the filamentary layer is superposedon the web layer and needled together, it is difficult to obtain anintertwining effect, and the flexibility of the conveyor belt isdeteriorated. The needling of filamentary layer alone, which may be.referred to as preneedling, is sufficiently performed at a punchingdensity of -200 times per square centimeter. Also the punching densityof the needling of web layers alone is preferably no more than 30 timesper square centimeter. Such preneedling is not always required. Thepreneedling of the filamentary layer is carried out for the purpose ofremoving spots caused by tension and of opening the filaments.Subsequently, a web must be superposed, and needling of them togethershould be carried out.

The punching density of needling given to the filamentary layer with thetwo web layers superposed on its top and bottom is l00-600 times persquare centimeter, preferably 200-400 times per square centimeter. Whenthe punching density is less than 100 times per square centimeter, theresulting conveyor belt shows a tendency of reduced flexibility, andwhen it is more than 600 times per square centimeter, the longitudinalstrength of the conveyor belt tends to be reduced.

The punching density is also dependent, to a certain extent, on the sizeand configuration of the needle employed. The needle size normallyranges 0.5-1.3 mm., preferably 0.60.8 mm., in diameter, and the size isexpressed by height of its cross section. The barb configuration may betriangular, round, or square, but triangular is preferably used. Theundercut angle of the barb is 0-70, preferably l0-30, but angles outsidethe preferred range are usable so far as a sufficient intertwiningproperty can be imparted to the filamentary layer and web layers. Thepreferred keep-up height of barb ranges 0.2-0.4 mm., but heights outsidethe specified range are usable so far as the layers are imparted withsatisfactory intertwining property and fiber breakage is not aggravated.A standard number ofthe barb is 9.

The nonwoven sheet composed of a filamentary layer and two web layers,which is thus imparted with dimensional stability and intertwiningproperty, is then impregnated with an adhesive.

' styrene-butadiene rubber or a mixture thereof, as the adhesive any ofnatural, styrene-butadiene rubber, or vinylpyridine rubber or laticesthereof is usable, at an optional blend ratio. When the rubber coverconsists of more than one component in the above-mentioned combinations,it is preferred to use more than one component of the correspondingadhesive components. Vinyipyridine rubber-type adhesive is employed whenparticularly strong bonding is required between the rubber cover andcore body. However, since conveyor belts are mostly made of natural orSBR rubber, in most occasions natural, SBR, or vinylpyridine rubber orlatices thereof are used as the rubber component of adhesive.

The adhesive must be sufficiently infiltrating in the nonwoven sheet.The adhesive pickup by the infiltration is at least 20 wt. percent tothe nonwoven sheet, preferably at least 25 wt. percent. When the pickupis less than 20 wt. percent, the longitudinal strength and flexibilityof the belt are objectionably impaired.

The ideal state of distribution of the adhesive in the nonwoven sheet issuch that the adhesive is crosssectionally uniformly distributed, andevery monofiber constituting the nonwoven sheet is sufficiently fixed.Upon fixing of monofibers, the core body is imparted with strength andflexibility.

In order to impart strong adhesion between the nonwoven sheet as coreused and the cover rubber and between the filamentary layers and thestaple fiber layers, the adhesive preferably consists of the rubbercomponent and also a component having an affinity with the fibers(fiberphilic component), such as well known isocyanate compounds,resorcinformalin resin, epoxy compounds, ethylene-urea compounds,ethylene-imine compounds, phenolic resin, etc. is used. Rubberlatex-resorcin-formalin resin adhesives or rubber component-isocyanatecompound adhesives, such as triphenylmethane-4,4,4-triisocyanateadhesive, are particularly preferred. Specific content of thefiber-philic component in any adhesive composition is determined inaccordance with the materials of rubber cover and the fibers, whilenormally it is no more than 25 wt. percent to the rubber component,preferably no more than 15 wt. percent. The content is preferably keptto the allowable minimum, for improving the flexibility of conveyorbelt. With the increase in the content of fiber-philic component, thereis a tendency that less pickup of the adhesive composition byinfiltration achieves satisfactory result.

With a conveyor belt of the invention, it is not always necessary to mixa fiber-philie component into the adhesive composition, due to theanchoring effect of its specific construction. In the known conveyorbelts containing core body of woven sheets, if an adhesive compositioncontaining no fiberphilic component is used for bonding rubber coverwith the woven sheets, the peel strength is drastically reduced.Whereas, in the conveyor belt of the invention, even when an adhesivecontaining no fiber-philic component is used to bond the rubber overwith core body by pressing, the peel strength of practical level isretained. Thus the conveyor belt of the invention exhibits practicablelevel of peel strength, when its filamentary layer and web layers areformed of polyester or polypropylene fibers and the nonwoven sheet isbonded with the rubber cover using an adhesive composed of rubbercomponent only, in the absence of cheap and suitable adhesive componenthaving affinity to such fibers.

However, in case an adhesive containing a fiber-philic component isused, the weight ratio of the component to the rubber component must bewithin the range specified in the above. Otherwise, the interfibrousfixing advances excessively as already mentioned, and the flexibility ofthe belt is remarkably impaired.

The adhesive can be used in the form ofa solution in a solvent, such ashydrocarbon solvents including gasolin, hexane, and petroleum ether;benzene solvents including benzene, toluene and xylene; ketone solventssuch as methyl ethyl ketone and diethyl ltetone; or in rubber-latexform. When a fiber-philic component is added as one component of theadhesive, isocyanate compounds are preferred for organic sol vent typeadhesive compositions, and resorcin-formalin resins are preferred forlatex type adhesive compositions. In case of dissolving rubber inorganic solvent, it is preferred that the rubber should be fullymasticated.

It is of course permissible to blend with the adhesive composition,various reinforcing agent, vulcanization agent, and additives, such ascarbon black, sulfur, zinc flower, stearic acid, calcium carbonate,processing oil, etc., and/or various promotor and antioxidant, inaccordance with the accepted practice.

Unnecessarily high viscosity of the adhesive solution should be avoided,since such will prevent uniform infiltration of the adhesive into thenonwoven sheet. Appropriate viscosity is dependent on thickness (weight)of the nonwoven sheet, but normally is not higher than 150 p.i.g.,preferably not higher than I p.i.g. When the nonwoven sheet isrelatively thick (800 g./m. or above in weight), the viscosity ofadhesive solution is necessarily not higher than 100 p.i.g.

The conveyor belt of the invention is manufactured, on the principle, inaccordance with ordinary method. However, the manufacture of theconveyor belt of this invention is different from that of conventionalconveyor belts in the following point.

In the manufacture of known conveyor belts, woven sheets are used as thecore. Accordingly, the woven sheets must be subjected to a rubberizingstep by friction in advance. In contrast, no rubberizing step isnecessary in the process of this invention.

First the nontwisted and noncrimped filaments are wound on a bobbinmounted on a creel stand, and the filaments are withdrawn from thebobbin as flatly paralleled, towlike filament of several thousands toseveral tens of thousand deniers. On the top and bottom surfaces of thusparalleled filaments, then web layers are superposed, and the threesheets are together fed into a needle locker. Or, multiple strands offilamentary yarns may be once wound onto warpers, and wherefrom suppliedto the needle locker.

At the needle locker, the flatly paralleled towlike filaments and weblayers are subjected to necdling, under a tension of at least 2 g. per1,200 deniers of the filaments, preferably at least 5 g. in that case,the tension ofmaximum feasible is preferred, since higher tensionreduces unevenness in tension distribution among the yarns in thefilamentary layer. Thus a product of better uniformity can be obtainedunder the higher tension. When the tension is too low, fiber orientationis disturbed during the necdling, and the longitudinal strength of thebelt are impaired.

As aforesaid, it is permissible to perform the first or preneedling onthe filamentary layer composed of flatly paralleled, towlike filamentsand/or web layer or layers; and then to perform the second needling onthe layers integrally superposed.

Thus needled nonwoven sheet composed of filamentary layer and web layersis then impregnated with an adhesive, to a point of sufficient pickup.

The sheet is then dried, and baked for 2-10 minutes at a temperature of100-480 C., preferably l30-l60 C., to be converted to the core body inaccordance with the invention.

The core is then interposed between cover rubber, and passed for l030minutes under a pressure of 1040 kg./cm.,

normally kgJcm. at a temperature of 120-180 C., preferably l40l50 C., tocomplete the conveyor belt of the invention.

In the above process of manufacture, the filaments constituting thefilamentary layer, the webs forming the web layers, weight ratiosbetween the two, needling conditions,

size and configuration of needle, and. adhesive composition, etc. aresimilar to those fully described as to the conveyor belt oftheinvention.

The conveyor belt of the invention thus possesses novel construction andexcellent performance. That is, the core body of the belt must have thespecific components and construction as follows:

1. A synthetic chemical filamentary layer in which nontwisted andnoncrimped filaments form a layer as paralleled in longitudinaldirection;

2. Two carded or random web layers of crimped staple fibers, which aresuperposed on the top and bottom of the filamentary layer;

3. Nonwoven sheet formed by the above three layers integrated byneedling;

4. The core body formed by impregnating the nonwoven sheet with anadhesive.

The satisfactory numerical ranges and other limitative factors of theabove composition are as described in the foregomg.

And, the criticality of each constituent of the conveyor belt of thisinvention can be summarized as follows:

The filamentary layer alone cannot form a dimensionally stable core bodybecause the filaments have no intertwining property. Therefore anyconveyor belt having the filamentary layer alone as the core body isimpracticable.

Whereas, conveyor belts having web layers alone as the core body cannotsatisfy the requirements on flexibility and longitudinal strengthincurred on a conveyor belt. Satisfactory core body is formed bysuperposing two web layers on the two surfaces of the filamentary layer.lf only one web layer is used, the resulting conveyor belt exhibits onlyunsatisfactory longitudinal strength, flexibility, and rubber peelstrength. Also is the nonwoven sheet composed ofa filamentary layer andtwo web layers is not impregnated with an adhesive, the conveyor beltusing such a sheet as the core shows poor flexibility and rubber peelstrength, and unsatisfactory for practical use.

Conveyor belts with the core meeting all the requirements of theinvention except that it not needled, show markedly reduced longitudinalstrength, flexibility and rubber peel strength, and unsatisfactory forpractical use.

Furthermore, the advantages of the subject conveyor belt can beenumerated as follows:

1. While the conveyor belt with monoply, woven fabric as the core has atoo great elongation and pliability for practical use, the belt of theinvention has a small. elongation and suitable hardness with the monoplycore of specified structure.

2. Therefore, the belt of the invention is thinner and lighter in weightcompared with the belt with a core of laminated, several layers of wovenfabric. Consequently the former tends to be along the pulley, even whenthe pulley diameter is small.

3. While the strong adherability with rubber is an essential requirementfor the conveyor belt using multi-ply woven fabrics as the core, thecore body in accordance with the invention exhibits excellentadherability with rubber, because the core is monoply and has web layersas its constituent.

4. in case of conveyor belt with woven core, occasionally braker is usedseparately for protecting the woven core, particularly from impact, etc.Whereas, the filamentary layer in the core of the subject conveyor beltis sufficiently protected by the web layers.

5. in case of conveyor belts with woven core, the core is prepared fromfibers through numbers of steps with much labor such as spinning,twisting, and weaving. Furthermore, the core is subjected to dipping ofadhesive agent such as resorcin-formalin latex and rubber friction, andthereafter pressed with rubber cover.

Whereas, the conveyor belt of the invention can be manufactured byremarkably shortened steps such as forming the nonwoven sheet, treatingthe same with a rubber-type adhesive, and pressing it with rubber cover.Furthermore, the belt can be continuously manufactured in accordancewith the present invention.

6. The object of the invention being to provide the conveyor belt withmonoply core, however, multi-ply core as of ordinary woven core may alsobe formed if desired.

Hereinafter the invention will be explained with reference to workingexamples.

EXAMPLE 1 Nontwisted and noncrimped polyvinyl alcohol syntheticfilaments of the size 1,200 dr./200f. (the strength-elongation of theyarn: 8.4 Kg.X l 3 percent) were paralleled over a width of 30 cm. at aratio of 16 strands per 1 cm. (214 g./m. by weight), and subjected to aneedling of 50 times per square centimeter to impart intertwiningproperty to the filaments. Then each 50 g./m. of two webs of polyvinylalcohol synthetic fiber (2 deniers in size and 51 mm. in fiber length;the strength-elongation of the single fiber: 5.5 g./dr. 14.5 percent)were superposed on the top and bottom of the filamentary layer, andsubjected to a needling of 300 times per square centimeter. Thereafterthe integrated sheet was impregnated with a resorcin-formalin latex(hereinafter abbreviated as RF L) as an adhesive agent. RFL was preparedas follows:

The molar ratio of RIF was 1:1; RF concentration was 6 percent, and 4percent of caustic soda to the R was added. The adhesive composition wasallowed to stand for 6 hours at an ambient temperature of 20 C., to ageRF in the latex. To the resulting aqueous solution of RF resin, a latexwas added at a weight ratio of 15/100. The latex was obtained by mixingstyrene-butadiene copolymer latex, Nipol L X 102 withvinylpyridine-styrene-butadiene copolymer latex, Hycar 2518 F at aweight ratio of 3:1. Both of said two latices were products manufacturedby Japanese Geon Company. After addition of the latex, the compositionwas allowed to stand for 16 hours at 20 C. to complete the aging. Theadhered amount of the adhesive agent was 20.4 percent. The fabric wasbaked for 4 minutes at 160 C. The so obtained nonwoven fabric exhibitedstrength of l kg. per width of 1 cm. in the paralleling direction of thefilaments. On both surfaces of the so obtained core body, cover rubberof the following composition was superposed and the entirety was pressedat 150 C. for minutes.

Composition ofthe cover rubber was as follows.

Component Parts by weight Naturai rubber 40 Styrene-butadiene rubber 60Carbon black 50 Zinc flower 5 Stearic acid 2.8 Sulfur 2.2 Promoter 1Aging resistant agent 1 The obtained conveyor belt was subjected to aflexing test by a Scott's flexing tester (manufactured by UejimaSeisakush of Japan), the belt withstood flexing of 500,000 times untilcausing separation, exhibiting strength-elongation .of 14 Kg./cm. l6.2percent and rubber peel strength of 20.2 kg./Width of cm.

The measurements of strength-elongation, flexibility and rubber peelstrength were performed as follows: Strength-elongation A 3-cm. wide and20-cm. long piece was cut off from the sample conveyor belt, and pulledat a Kg.Xof 5 cm./min., with a clutching interval of 10 cm. Thusmeasured value, for example 225 Kg./cm. l6.5 percent of Run No. 1,denotes that strength per width of 1 cm. of the belt was 225 kg. andelongation of the belt at that time was 16.5 percent as compared withthe original length. The strength-elongation was measured by a generaltensile tester (manufacture by Shimazu Seisakusho ofJapan, Autograph18-2000).

Flexibility The test was performed with Scott's flexing tester(manufactured by Uejima Seisakusho, Japan).

Test Specimen: 2.5 cm. in width and 35 cm. in length The test piece wasmounted on a grooved wheel of 25 cm. in diameter, and its two ends werefixed. The angle at the circumference at a contact point of the groovedwheel to the test piece was Then the piece was caused to performrepetitive, continuous bending along the circumference of the groovedwheel, at a reciprocation rate of times per minute over a reciprocatorydistance of 134 mm., under a load of 50 kg.

The number of flexing at which an abnormality was observed in the testspecimen was recorded as the norm of flexing performance.

Rubber peel strength Test Specimen: 2.5 cm. in width and 20 cm. inlength The rubber cover was peeled off from the core of the specimen bya short distance, and the tips of the two were interposed between clampsof a belt peel tester and pulled to each opposite direction at a rate of5 cm./min. The tensile load under which the peeling distance reached 7.5cm. was recorded by a recorder and the rubber peel strength wascalculated therefrom. The measured values showed a wavy graph whenplotted and arithmetic mean of each crest point of said wavy portion ofthe curve was calculated, which was made a peel strength.

The measuring was done using a belt peel tester (manufactured by UejimaSeisakusho, Japan).

EXAMPLE 2 Nontwisted and noncrimped polyvinyl alcohol syntheticfilaments of the size 4,800 dr./800f. (the strength-elongation of theyarn: 32.5 Kg. (13 percent) were paralleled over a width of 30 cm. at aratio of 10 strands per 1 cm. (534 gJm. by weight), and subjected to aneedling of 100 times per square centimeter. Then each 95 g./m. of twowebs of polyvinyl alcohol synthetic fiber (2 deniers in size and 51 mm.in fiber length; the strength-elongation of the single fiber: 5.5 g./dr.l4.5 percent) were superposed on the two surfaces of this filamentarylayer, and the three layers were integrated by a needling of550 timesper square centimeter.

After needling, the resultant nonwoven sheet was impregnated with RFLwhose composition was the same as that in example 1. The product showeda strength of 220 kg./l cm. in the direction of filaments. Pressingrubber cover thereonto by the method same as that in example 1, theresulting conveyor belt was subjected to a peeling test. High bondingstrength between the core and rubber cover was demonstrated by the peelstrength of 21 kg./2.5 cm. in width. The monoply belt withstood theflexing of 200,000 times in the bending test. Thus the core was provento have an excellent performance as the core of conveyor belt, and thebelt showed strength. of 220 kg. and elongation of 17.1 percent.

The strength-elongation, flexibility and rubber peel strength weremeasured in identical manner with those described in example 1.

EXAMPLE 3 Nontwisted and noncrimped Vinylon filaments of the size 4,800dr./2,000f. (the strength-elongation of the yarn: 33.6 Kg. l4.l percent)were paralleled at a ratio of 4 strands per the width of 1 cm. (214g./m. by weight), and subjected to a needling of 25 times per squarecentimeter.

Between two of the above filamentary layers, a Vinylon web of 50 g./m.(2 dr. 5l mm.: the strength-elongation of the single fiber: 5.5 g./dr.14.5 percent) was inserted, and further on the top and bottom of thesandwiching layers, same webs were superposed and subjected to needling.The punching density of the needling was 200 times per squarecentimeter. Subsequently the layers were bonded with an acrylate latexin the accepted manner. The adhesive pickup was 25 percent, and theresultant nonwoven fabric had a strength of 230 kg./cm. in the directionoffilaments.

The strength-elongation was determined by the same method as describedin example 1.

EXAMPLE 4 Nontwisted and noncrimped polyvinyl alcohol syntheticfilaments of the size 1,200 dr./200f. (the strength-elongation of theyarn: 8.4 kg. 13 percent) were paralleled over a width of 30 cm., at aratio of 32 strands per width of 1 cm. (427 g./m. by weight), and in themeantime, the top and bottom surfaces of the layer were superposed witheach one web of polyvinyl alcohol synthetic fibers (80 g./m. in weight,7 deniers in size, and 51 mm. in fiber length; the strength-elongationof the single fiber: 6.1 g./dr. l6.2 percent). The layers were subjectedto a needling of 300 times per square centimeter, and then treated witha RFL adhesive as follows: The mol ratio of R/F was l/l; RFconcentration was 6 percent, and 4 percent ofcaustic soda to the R wasadded. The adhesive composition was allowed to stand for 6 hours at anambient temperature of 20 C., to age RF in the latex. To the resultingaqueous solution of RF resin, a latex was added at a weight ratio of15/300. The latex was that obtained by mixing styrene-butadienecopolymer latex, Nipoi L X 102 and vinylpyridine-styrene-butadienecopolymer latex Hycar 2518 F at a rate of 3:1. After addition of thelatex, the composition was allowed to stand for 16 hours at 20 C. tocomplete the aging. Thus obtained RFL solution (viscosity: 5 poise) wassufficiently impregnated in the above nonwoven fabric. The fabric wasbaked for 4 minutes at 160 C. The RFL pickup of the nonwoven fabric was25.7 percent.

Thus obtained nonwoven fabric was pressed at 20 l g./cm. of presspressure for 20 minutes at 150 C., as interposed between rubber coversof 1.6 mm. in thickness.

The performance of thus obtained conveyor belt of the invention was asindicated in Table i as Run No. l.

Separately, nontwisted and noncrimped filaments of polyvinyl alcoholsynthetic fiber of the size 1,200 dr./200f. (the strength-elongation ofthe yarn: 8.4 Kg. l3 percent) were paralleled at the ratio of 32 strandsper 1 cm. width (427 g./m. by weight), and subjected to a preneedling ata punching density of times per square centimeter on its both surfaces.Each 80 g./rn. of two webs formed of polyvinyl alcohoi synthetic fiber(7 deniers in size and 51 mm. in fiber length; the strength-elongationof the single fiber: 6.1 g./dr. l 6.2 percent) were superposedrespectively on top and bottom of the filamentary layer, and togethersubjected to another needling at a punching density of 300 times persquare centimeter. Thus formed nonwoven sheet was subsequently treatedin the manner identical with the procedures described in the above.Performance of the conveyor belt thus obtained is given as Run No. 2 inTable i. As regards the flexibility, the symbol 0 shows that theconveyor belt was not changed, and the symbol x shows that separationoccurred.

In the same Table, Run Nos. 3 though 17 and 20 through 22 are thecontrols, the conveyor belts being within the scope of this inventionexcept in the point described in the second column.

The strength-elongation, flexability and rubber peel strength weremeasured by the identical methods with those described in example 1,except that in the flexibility test, a grooved wheel of 35 mm. indiameter was employed.

As the covering, the rubber of following composition was Sulfur Promoter1 Aging resistant agent i TABLE I Flexibility (thousand times) Rubberpeel Strength Run No. Conveyor belt 1. Each single web was super posedon the top and bottom of filamentary layer and needied together.

2 The filamentary layer alone was needled in advance and then superposedwith two webs and needled together.-

3 The core body was formed of webs alone.

4 Only one web was superposed on the filamentary layer.

5 Twisted filaments were used to form the filamentary layer (100'I./m.).

6. Crrmped filaments were used to form the filamentary layer (22crimps/2.54 cm.).

7. Tension exerted on the filamentary layer was low (tensionfilament=1.2 g./l., 200

r). 8 The weight ratio 01 web layers to filamentary layer was more than1 :1 (500 g./m. :1/1.17; Belt thickness: 4.8 mm.; Core thickness:

9. The weight ratio of web layers to filamentary layer was less than 1:5 (60 g./m. 1/7.1; Belt thickness: 4.0 mm.; Core thickness: 0.8 mm.).

10. The filamentary layer was excessively heavy (Filameutary layer: 1050g./m. Web layers: 270 g.ln1. Belt thickness: 4.8 mmx, Cora thickness:1.7 mm.

11- Pro-needling oi web layers was periormed at a punching density oftimes/emf.

12- The layers were joined by means of an adhesive alone, withoutneedling.

i3. Punching density of the needling was less than times/cm. (80times/cmfl).

14- Punching density 01 the needling was more than 600 times/cm. (720times/crnfl).

15 No adhesive was used 16 Pick-u oi the adhesive was less t an 20% (RFL14%).

17. In the adhesive composition,

the content 01 non-rubber component was greater than 25/100 (RF/L ratio:30/100).

18. No non-rubber component (fiber-phiiic component) was added to theadhesive composition (RF/L ratio:

19- Desmodur R (an isocyanate 221x17. 8 150 o 18. 3

type compound, product of Farbenfabriken Bayer A.G.) was blended in theadhesive at a ratio of 12% to the rubber component (added to dissolvedrubber).

20. Dcsrnodur R was blended in the adhesive at a ratio oi 30% the rubbercomponent (added to dissolved rubber).

21, The viscosity oi adhesive was too high to infiltrate into thenon-woven fabric (dissolved rubber having a viscosity of 1750 p.i.g.).

22. The combination of adhesive and the rubber composition oi coveringwas unsuitable (covering was of ncoplenc type rubber).

23. The viscosity of adhesive was low enough to be fully infiltrate thenon-woven fabric (dissolved rubber having a viscosity of 7 p.i.g.).

K cm.

A iLhe adhesive, a composition identical with that of rubber cover wasdissolved in gasolinetoluenc solution (1:1) for rubber. In the case,only drying was carried out and no baking was carried out.

EXAMPLE Conveyor belts were manufactured in the manner described inexample 4, except that the synthetic fiber material of the filamentarylayer and web layers was replaced by those indicated in Table II. Theirlongitudinal strength-elongation, flexibility and rubber peel strengthare given also in Table II.

The measurement of the properties was performed by the testing methodsidentical with those described in example 4 1. A conveyor belt withinthe scope of this invention was prepared in the manner described inexample 4. The weight of the core body treated with RFL adhesive, aftersubsequent drying and baking, was 738 g./m. and that of the conveyorbelt bonded with the rubber cover by pressing was 4,580 g./m. The beltwas 4.2 mm. in thickness.

2. Separately, plain woven canvas of the structure 1200 d/3X848 d/2 45strands X27 (5 cm. in width) and of the weight 505 g./m. was preparedfrom polyvinyl alcohol synthetic filaments 1,200 dr./200f. (thestrength-elongation of the yarn: 8.4 kg.Xl3 percent) as the woof andnylon filaments 840 dr./ l60f. (the strength elongation of the yarn: 6.4kg. 22.5 percent) as the warp, and using monopoly of the plain wovensheet as the core, a conveyor belt was prepared in As to the foregoingfour conveyor. belts, longitudinal strength-elongation, elongation undertension corresponding to one-tenth of belt strength, flexibility,metallic tool joining efficiency, rubber peel strength, impact strengthand fatigue property were measured, with the results as given in TableIII.

The longitudinal strength-elongation, flexibility and rubber peelstrength were measured by the methods described in example l. Otherproperties were measured as follows: Elongation under tensioncorresponding to one-tenth of belt strength I it was measured inaccordance with the same process of measuring longitudinalstrength-elongation except tension corresponding to one-tenth of thebelt strength was imposed on the belt. Normally, a conveyor belt is madeto run while being imposed with tension corresponding to one-tenth toone-sixteenth. Therefore, said elongation under tension corresponding toone-tenth of belt strength becomes one important characteristics of thebelt.

Metallic tool joining efficiency The two 4.5-cm. wide and l5-cm. longsamples conveyor belts were jointed with No. 27 lacing (the shape of thelacing was that defined in 115 B 1851), and the joint portion was brokenby exertion of tension as in the strength-elongation test same as inexample 1 except the distance between clamps was 20 cm. and the tensilespeed was 10 cm./min. The ratio between the breaking strength and thestrength of the sample belt was recorded as the metallic tool joiningefficiency. Impact strength The sample was fixed at both ends, andsubjected to a tension corresponding to one-twelfth of the strength ofsample belt. To the sample then 9 kg.-m. per blow of impact energy wasexerted with an iron piece having a 3-mm. long blade, totaling 500blows. The strength of the belt measured before and after the impact wasexpressed by a percentile value. Fatigue property A l0-cm. wide and 4-m.long sample belt was caused to run between two pulleys of 30 cm. indiameter under the following conditions, and the strength variationbefore and after the running was expressed by a percentile value:

the manner described in example 4. The resultant belt was Belt tension:one-twelfth ofbelt strength 4,400 g./m. in weight and 4.1 mm. inthickness. Running velocity: l,200 m./min.

3. Separately, a woven fabric of polyvinyl alcohol synthetic Runningperiod: 2 months.

TABLE III Elongation under tension Longitudinal corres. Metallicstrengthto Mo tool Rubber elongation of belt Flexibility joining peelImpact Fatigue (kg./cm-X strength (thousand efficienc strength strengthresistance perteit) (percent) times) (percent kg./2.5 em.) (percent)(percent) Conveyor belt of the invention 22BX16. 5 0. 4 500 o 36 20. 493. 8 84. 8 Conveyor belt with monoply, woven core 207x20. 6 3. 1 500 o34 15. 4 38. 3 89. 1 Conveyor belt with iourply, woven core... 221x20 11.0 280 X 30 14. 2 53. 1 70. 5 Conveyor belt in which the filamentarylayer was replaced by woven fabric 223x21. 5 3. 3 350 X 39 20. 4 95. 289.5

spun fiber (2 dr. 5l mm.: the strength-elongation of the single Weclaim: fiber 5.5 g./dr.Xl4.5 percent) of the structure 1. A conveyorbelt in which the rubber cover is bonded to a 10/4 X 10/4 coreimpregnated with an adhesive, characterized in that the core is anonwoven sheet consisting of a filamentary layer of n Strand X 25strands (5 cm 1 Wldth) 0 longitudinally and flatly paralleled filamentsselected from and of the weight 450 g./m. was treated with RFL adhesivein synthetic filaments and chemical filaments in the form of tows themanner described in example 4. Then rubber of the same a web layers ofstaple fibers which are superposed on the composition as the coverrubber was rubbed in the wov n top and bottom ofthe filamentary layer,said filamentary layer sheet, Four sheets of this obtained woven fabricwere being composed Of substantially nontwrsted and noncrimpedlaminated, and bonded with the rubber cover by pressing as filamentsWllh the Web layers being Composed of cnmped described in example 4.Thus a conveyor belt with the core formed of four-ply woven sheet wasmanufactured, which had a weight of6.680 g./m. and a thickness of 6.0mm.

4. A conveyor belt similar to that manufactured in the experiment 1above was manufactured, except that its filamentary layer was replacedby the plain woven sheet employed in 2 above. The core formed of theplain woven sheet with two web layers superposed on its two surfaces hada weight of 856 g./m. after RFL treatment. The belt had a weight of4,700 g./m. and a thickness of4.3 mm.

pie fibers, said filamentary layer and the web layers being superposedand integrated by needling to produce entanglement between the filamentsand fibers the nonwoven sheet being sufficiently impregnated with arubber-type adhesive, the weight ratio of the filamentary layer to theweb layers being within the range of5:l to 1:1.

2. The conveyor belt of claim 1, in which the fiber material forming thefilamentary layer and web layers is selected from the group consistingof polyesters, polyvinyls, poiypropylenes and high tenacity rayon.

3. The conveyor belt of claim 1, in which the filaments forming thefilamentary layer are substantially continuous, the staple fibersforming the web layers are at least 40 mm. in length, and the size ofboth materials ranges from l,45-7 denier.

4. The conveyor belt of claim 1, in which the filamentary layer issubjected to a preneedling ofa punching density ranging from l-200times/emf.

5. The conveyor belt of claim 1, in which the web layers are subjectedto a preneedling at a punching density of no more than 30 times/emf 6.The conveyor belt of claim 1, in which the filamentary layer and weblayers are subjected to a needling at a punching density of 100-600times/cm?- 7. The conveyor belt of claim 1, in which the adhesive pickupof the core is at least percent by weight,

8, The conveyor belt of claim 1, in which the adhesive is composed of atleast one rubber component and at least one fiber-philic componentselected from group consisting of an isocyanate compound,resorcin-formalin resin, epoxy compound, ethylene-urea compound,ethylene-imine compound and phenolic resin.

9. The conveyor belt of claim 8, in which the fiber-philic component inthe adhesive is present in an amount of no more than 25 percent byweight based on the rubber component.

10. The conveyor belt of claim 1, in which the adhesive contains asolvent selected from the group consisting of hydrocarbon-type,benzene-type, and ketone-type solvents.

11. The conveyor belt of claim 1, in which the adhesive has a viscositynot higher than p.i.g.

12. The conveyor belt of claim 1, wherein said web layers are composedof random staple fibers.

13. The conveyor belt of claim 1, wherein said web layers are composedofcarded staple fibers.

2. The conveyor belt of claim 1, in which the fiber material forming thefilamentary layer and web layers is selected from the group consistingof polyesters, polyvinyls, polypropylenes and high tenacity rayon. 3.The conveyor belt of claim 1, in which the filaments forming thefilamentary layer are substantially continuous, the staple fibersforming the web layers are at least 40 mm. in length, and the size ofboth materials ranges from 1.45-7 denier.
 4. The conveyor belt of claim1, in which the filamentary layer is subjected to a preneedling of apunching density ranging from 15-200 times/cm.2.
 5. The conveyor belt ofclaim 1, in which the web layers are subjected to a preneedling at apunching density of no more than 30 times/cm.2.
 6. The conveyor belt ofclaim 1, in which the filamentary layer and web layers are subjected toa needling at a punching density of 100-600 times/cm.2.
 7. The conveyorbelt of claim 1, in which the adhesive pickup of the core is at least 20percent by weight.
 8. The conveyor belt of claim 1, in which theadhesive is composed of at least one rubber component and at least onefiber-philic component selected from group consisting of an isocyanatecompound, resorcin-formalin resin, epoxy compound, ethylene-ureacompound, ethylene-imine compound and phenolic resin.
 9. The conveyorbelt of claim 8, in which the fiber-philic component in the adhesive ispresent in an amount of no more than 25 percent by weight based on therubber component.
 10. The conveyor belt of claim 1 in which the adhesivecontains a solvent selected from the group consisting ofhydrocarbon-type, benzene-type, and ketone-type solvents.
 11. Theconveyor belt of claim 1 in which the adhesive has a viscosity nothigher than 150 p.i.g.
 12. The conveyor belt of claiM 1 wherein said weblayers are composed of random staple fibers.
 13. The conveyor belt ofclaim 1 wherein said web layers are composed of carded staple fibers.